This invention relates in general to refrigeration systems and in particular to a holding plate for a marine refrigeration system.
In a standard refrigeration system a refrigeration fluid such as freon is recirculated through a compressor, condenser and evaporator. The fluid is liquified in the condenser and vaporized in the evaporator coils by heat absorbed from a cooling compartment, usually the interior of a refrigerator. Standard systems also typically include some arrangement for filtering and drying the fluid as well as valves to control the movement of the fluid. In most standard refrigerators, the evaporator is a rectangular, flat unit formed from sheet metal with the fluid flowing through the evaporator in channels stamped in the metal. The fluid can be guided either in the channels themselves or in a tube held within the channel.
Marine refrigerators designed for use on comparatively small watercraft must meet design criteria not present in standard household refrigerators. First, a marine unit usually does not have a continuous power supply. Rather, the system can cool only when the main boat engines are operating. It is impractical to run the engines continuously only to provide refrigeration and it is inconvenient, although less costly, to run the engines at regular intervals throughout the day. Due to the limited space available on most boats, a marine refrigerator must also be compact. Another important consideration is that the refrigerator be able to make ice quickly while at the same time having a good cold storage capacity to maintain perishable foods cooled during extended periods where there is no power.
One marine refrigeration unit presently available uses a freezing compartment oriented vertically along the side of a cooling compartment that includes an evaporator. If a liquid is used in the cooling compartment to transmit heat, the side mounting avoids the insulating effect of an air bubble which can form at the top of the liquid. This unit is located in an insulating compartment. To make ice, a plastic divider is lowered into the freezing compartment when it is filled with water.
Another unit is essentially a small household refrigerator. As such it is not especially well suited to marine use except that it is compact. One difficulty is that the cooling is directed generally uniformly into the entire cooling compartment. As a result, the entire refrigerator must be cooled substantially before ice can be made. This ice making process is slow. The unit also has only conventional capabilities for storing coldness. Some factors influencing the storage capacity are the insulating quality of the compartment, the frequency of use of the unit, the nature and quantity of items stored in the refrigerator, and the ambient air temperature. In practice, both of these units will not make ice quickly and require operation of the engines for either an extended period of time or on at least several occasions each day. Another difficulty with the "vertically oriented" refrigeration unit described above is that it is frequently difficult to remove ice cubes from the compartment once they are formed.
It is therefore a principal object of this invention to provide a refrigeration unit that has a short running cycle and a fast freezing capability.
Another object of the invention is to provide such a refrigeration system that is compact and has a good cold storage capacity.
A further object of this invention is to provide a refrigeration system with the foregoing advantages that also creates two temperature zones, one suitable for fast freezing and one suitable for ordinary refrigeration.
A further object is to provide a refrigeration system with the foregoing advantages that has a simplified construction and a competitive cost of manufacture.